Heart valves, such as the mitral, tricuspid, aortic and pulmonic valves, are sometimes damaged by disease or by aging, resulting in problems with the proper functioning of the valve. Heart valve problems generally take one of two forms: stenosis, in which a valve does not open completely or the opening is too small, resulting in restricted blood flow; or insufficiency, in which blood leaks backward across a valve when it should be closed. Valve replacement may be required in severe cases to restore cardiac function. In common practice, repair or replacement requires open-heart surgery with its attendant risks, expense, and extended recovery time. Open-heart surgery also requires cardiopulmonary bypass with risk of thrombosis, stroke, and infarction.
Mitral valve insufficiency results from various types of cardiac disease. Any one or more of the mitral valve structures, i.e., the anterior or posterior leaflets, the chordae, the papillary muscles or the annulus may be compromised by damage from disease or injury, causing the mitral valve insufficiency. Typically, in cases where there is mitral valve insufficiency, there is some degree of annular dilatation resulting in mitral valve regurgitation. Mitral valve regurgitation occurs as the result of the leaflets being moved away from each other by the dilated annulus. Thus, without correction, the mitral valve insufficiency may lead to disease progression and/or further enlargement and worsening of the insufficiency. In some instances, correction of the regurgitation may not require repair of the valve leaflets themselves, but simply a reduction in the size of the annulus. A variety of techniques have been used to reduce the diameter of the mitral annulus and eliminate or reduce valvular regurgitation in patients with incompetent valves.
Current surgical procedures to correct mitral regurgitation in humans include, a number of mitral valve replacement and repair techniques. Valve replacement can be performed through open-heart surgery, open chest surgery, or percutaneously. The native valve is removed and replaced with a prosthetic valve, or a prosthetic valve is placed over the native valve. The valve replacement may be a mechanical or biological valve prosthesis. The open chest and percutaneous procedures avoid opening, the heart and cardiopulmonary bypass. However, the valve replacement may result in a number of complications including a risk of endocarditis. Additionally, mechanical valve replacement requires subsequent anticoagulation treatment to prevent thromboembolisms.
As an alternative to valve replacement, various valve repair techniques have been used including quadrangular segmental resection of a diseased posterior leaflet, transposition of posterior leaflet chordae to the anterior leaflet, valvuloplasty with plication and direct suturing of the native valve, substitution, reattachment or shortening of chordae tendinae, and annuloplasty in which the effective size of the valve annulus is contracted by attaching a prosthetic annuloplasty ring to the endocardial surface of the heart around the valve annulus. The annuloplasty techniques may be used in conjunction with other repair techniques. Typically annuloplasty rings are sutured along the posterior mitral leaflet adjacent to the mitral annulus in the left atrium. The rings either partially or completely encircle the valve, and may be rigid, or flexible but nonelastic. All of these procedures require cardiopulmonary bypass, though some less, or minimally invasive techniques for valve repair and replacement are being developed.
Although mitral valve repair and replacement can successfully treat many patients with mitral valve insufficiency, techniques currently in use are attended by significant morbity and mortality. Most valve repair and replacement procedures require a thoracotomy, to gain access to the patient's thoracic cavity. Surgical intervention within the heart generally requires isolation of the heart and coronary blood vessels from the remainder of the arterial system and arrest of cardiac function. Open chest techniques with large sternum openings are typically used. Those patients undergoing such techniques often have scarring retraction, tears or fusion of valve leaflets, as well as disorders of the subvalvular apparatus.
Recently, other surgical procedures have been provided to reduce the mitral valve annulus using a less invasive surgical technique. According to this method, a prosthesis is transvenously advanced into the coronary sinus and deployed within the coronary sinus to reduce the diameter of the mitral valve annulus. The prosthesis then undergoes a change within the coronary sinus that causes it to assume a reduced radius of curvature, and as a result, to reduce the circumference of the mitral valve annulus. This may be accomplished in an open procedure or by percutaneously accessing the venous system by one of the internal jugular, subclavian or femoral veins.
While the coronary sinus implant provides a less invasive treatment alternative, the placement of the prosthesis within the coronary sinus may be problematic for a number of reasons. Sometimes the coronary sinus is not accessible. The coronary sinus on a particular individual may not wrap around the heart far enough to allow enough encircling of the mitral valve. Also, leaving a device in the coronary sinus may result in formation and breaking off of thrombus that may pass into the right atrium, right ventricle and ultimately the lungs causing a pulmonary embolism. Another disadvantage is that the coronary sinus is typically used for placement of a pacing lead, which may be precluded with the placement of the prosthesis in the coronary sinus.
It would be desirable, therefore, to provide a method and device for reducing cardiac valve regurgitation that use minimally invasive surgical techniques, and would overcome the limitations and disadvantages inherent in the devices described above.